Inkjet technology has expanded its application to high-speed, commercial and industrial printing, in addition to home and office usage. Coated, glossy inkjet recording material (or media) are available for such inkjet printing to produce high gloss prints with high brightness and high image quality comparable to that of off-set printing. It is desirable to make these inkjet recording material low cost so as to enable inkjet printing to be cost-efficient and to compete with traditional analog printing or other digital printing technologies, like laser printing or liquid electrophotography technologies.
Colorants, in inkjet inks, have advanced from dye molecules to pigment particles. Compared to dye-based inks, pigment-based colorants provide much better image performances. For example, light-fade or ozone fade of an image printed with pigment-based inks is much slower than that of an image printed with dye-based inks. With pigment-based inks, water resistance is also significantly improved because dye molecules are more readily dissolved into water than are pigment particles.
Coated inkjet recording materials (or media) have been developed for inkjet technology process, especially, for high-speed printers. In coated inkjet recording material (or media), image-receiving layer (i.e., layer onto which ink droplets are deposited) with small size particles and with high surface area incorporated therein as the major pigment, are often used. Such coating media often give excellent image quality and image permanence. Furthermore, some pigments can provide a coating layer with fast absorption and enough capacity for inkjet printing.
During inkjet printing process, it is often desired for the colorants in inks to be separated quickly after the ink drops are dispatched to recording substrate surface. Colorants are then kept at the substrate surface, while the solvents and other non-colorant components penetrate deeply into the recording substrate and, then, slowly dry through natural evaporation or through a heated drying process. Therefore, it is desirable that inkjet media possess a fast absorption rate to drive the ink vehicle quickly from top surface to the bulk of media, and high capacity to hold a large amount of ink vehicle. Inkjet coated media often use pigments with high surface area in the coating formulation and high coat weight to provide a good absorption rate and capacity. However, with the use of pigment-based inks, image defects and durability problems might be encountered. Such problems may include bad bleeding, coalescence, slow dry time, and poor rubbing or smear resistance. With the inclusion of pigments in the coating lacquers, general image quality and print quality is improved. Often, there are no obvious bleeding, coalescence, roller tracking marks, and other defects. However, images still look very “grainy”, i.e., a solid color area is often not uniformly filled and there are many darker color grains throughout the solid area.